All known natural calcitonin peptides contain an amino acid sequence of 32 amino acids. Salmon calcitonin, for example, has the following formula: ##STR1##
In U.S. Pat. Nos. 3,926,938, 4,062,815, 3,929,758, 4,033,940, 4,217,268 and 4,336,187 are disclosed improved syntheses of calcitonins including the salmon calcitonin referred to above.
The natural calcitonins include the salmon, eel, bovine, porcine, ovine, rat and human calcitonins. All of these have either serine or glycine at position number 2, either valine or methionine at position number 8, and either phenylalanine or tyrosine at position number 22.